Selective permeation of Ag+ ions from pyrosulfite solution through Nano-Emulsion Liquid Membrane (NELM) containing CYANEX 925 as carrier

A designed Nano-Emulsion Liquid Membrane (NELM) particles containing CYANEX 925 in kerosene as carrier, KSCN (potassium thiocyante) as internal stripping phase and span 80 as surfactant was prepared and used for the extraction of 9.27 x 10(-4) M Ag+ from pyrosulfite (Na2S2O5) solution. The parameters affecting the liquid-liquid extraction of Ag+ such as [CYANEX925], [pyrosulfite] and temperature were separately investigated. Ammonium hydroxide and thiourea with different concentrations were used to enhance the extraction efficiency of Ag+. The batch results indicate that the addition of ammonium hydroxide as complexing agent increased the extraction efficiency of Ag+ with CYANEX 925 from Na2S2O5 solution (up to E% = 75) while the addition of thiourea inhibited and strongly decrease the extraction process (E% = 25). The emulsion membrane was prepared and the NELM particles were characterized using dynamic light scattering (DLS) which indicated that the obtained nanoparticles have an average particle size of 29.9 nm. The studied fundamental parameters affecting the emulsion liquid membrane stability indicated that the optimum conditions were: emulsification speed = 8500 rpm, emulsification time = 10 min, stirring speed = 400 rpm, Span 80 = 3.5 % (w/v), organic: internal phase = 1:1, ELM: aqueous phase = 1:10 and permeation time = 10 min. The chemical permeation rate was found to be independent of [KSCN] in the internal phase and also of [Ag+] concentration in the aqueous feed solution. The demulsification of silver ions permeated through the NELM was achieved with 1 M NaBH4. An application on the selective recovery of silver ions from leached pyrosulfite solution of X-ray films wasted from radiology centers was carried out using the prepared NELM containing CYANEX 925 as carrier.